1. Field of the Invention
The present invention relates to a single-sided access device for 4F2 DRAM cell. More particularly, the present invention relates to a single-sided T-gate fin field-effect-transistor (FinFET) or single-gate FinFET with improved device control and access drive current, and a method for making the same.
2. Description of the Prior Art
As known in the art, dynamic random access memory (DRAM) is a type of random access memory that stores each bit of data in a separate capacitor within an integrated circuit. Typically, DRAM is arranged in a square array of one capacitor and transistor per cell. The transistor, which acts as switching device, comprises a gate and a silicon channel region underneath the gate. The silicon channel region is located between a pair of source/drain regions in a semiconductor substrate and the gate is configured to electrically connect the source/drain regions to one another through the silicon channel region.
A vertical double-gate fin field-effect-transistor (FinFET) has been developed for the next-generation 4F2 DRAM cell (F stands for minimum lithographic feature width). However, difficulties are frequently encountered in attempting to produce the vast arrays of vertical double-gate FinFET devices desired for semiconductor DRAM applications while maintaining suitable performance characteristics of the devices. For example, recently DRAM manufacturers face a tremendous challenge on shrinking the memory cell area as the word line spacing, i.e., the spacing between two adjacent word lines, continues to shrink. For high-speed DRAM applications, electrical coupling effect may be a problem as the spacing between two closely arranged word lines continues to shrink.
In light of the above, there is a strong need in this industry to provide a novel FinFET structure and the fabrication process thereof in order to avoid the aforesaid problems.